Electric generator with novel structure

ABSTRACT

The present invention provides a electric generator with novel structure, comprising two parts: a stator and a rotor. The stator has rectangle-section winding slots. The stator teeth have sectorial section. Slits are formed extending axially in the yoke and the magnet poles laid on the yoke in the rotor. The stator windings are made up of square-wave open rings with different pitches. The generator of the present invention has much less weight and smaller size, and the manufacturing process is simple, the consuming of copper and silicon steel sheets can be reduced, the efficiency is higher and energy can be saved.

TECHNICAL FIELD

The present invention relates to a multi-poles magneto electricgenerator having special windings, and is particularly adaptive forfrequency-changeable generators.

BACKGROUND ART

The electric generators of the prior art have some deficiencies, such aslow effective flux due to the large winding slots of the armature core;high internal resistance of the coil; high power consumption, resultingin temperature rising easily; long and overlapped end of the statorwindings; high eddy loss of the rotor and so on, which cause therestrictions on power output, materials cost, and size of the electricgenerator, consequently limit its application.

DISCLOSURE OF THE PRESENT INVENTION

The object of the present invention is to provide a novel electricgenerator which has smaller size, higher power output and saves thematerials to build it.

The present invention is an improvement to the structures of the statorand rotor of a conventional generator. The sections of the statorwinding slots are rectangular shape and the sections of the teeth aresectorial shape, thereby the effective area of the armature core isincreased and the total effective flux rises. The stator windings arecomprised of square-wave open rings with different pitches, so that thelengths of the end windings are decreased, and a lower internalresistance can be obtained. Magnet poles are laid on the magnet yoke ofthe rotor, and slits extending axially along the rotor are formed in themagnet poles and the magnet yoke. By means of these slits the iron lossof the generator decreases and using efficiency increases. The number ofthe stator slots and teeth is a multiple of 3, and the number of theteeth is a multiple of 3 times as much as the number of the magnetpoles. The distance between each two adjacent magnet poles laid on therotor surface equals to the width of one slot on the stator. Thethickness of the magnet poles laid on the rotor surface is equal to 7-8times as much as the width of the air gap between the rotor and stator.The magnet poles are fixed to the rotor surface with adhesive. The twoends of each of the magnet poles laid on the rotor are formed into wedgeshape and tightly held by wrap-edges of the rotor, and the portion heldby the wrap-edges is not greater than a quarter of the pole thickness.The length of the slits extending axially in the magnet poles and theyoke of the rotor is longer than a half of the axial length of themagnet pole. The width of the slits extending axially in the magnetpoles and the yoke of the rotor is 0.1 mm. Three branch windings belongto one set of windings corresponding to a pair of opposite magnet polesare arranged to embed in their respective slots on the stator withdifferent pitches as: crossing 5 teeth then crossing 1 tooth; crossing 3teeth then crossing 3 teeth; and crossing 1 tooth then crossing 5 teeth.Each 12 slots on the stator form a minimum unit. The windings betweenthe units can be connected in series, parallel or series-parallel mode.A plurality of winding sets overlapped in multiple layers are embeddedin the stator slots at a same position and the windings thereof can beconnected in series, parallel or series-parallel mode. With theirrespective displacement the three-phase windings are embedded in theirrespective slots of the stator. The winding arranged in each layer ineach slot of the stator comprises a single conducting wire.

Compared to the prior art, the present invention has the advantages suchas: smaller size, simpler manufacture process, saving on materials, andhigher generator efficiency etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of the generator of the presentinvention.

FIG. 2 is a schematic developed view of the stator windings of thepresent invention.

FIG. 3 is a schematic structural view of the rotor and its magnet polesof the present invention.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

As shown in FIG. 1, the present invention comprises two major parts:stator 1 and rotor 5. The sections of the winding slots 3 of the statorare rectangular and the sections of the teeth 2 of the stator 1 aresectorial. The windings 4 of the stator are embedded in the slots 3,respectively, and the structures thereof are square-wave open rings.Each layer of windings 4 is formed by a single conducting wire. Thenumber of the slots 3 and the teeth 2 is a multiple of 3. The number ofthe teeth is a multiple of 3 times as much as the number of the magnetpoles of the rotor 5. On the rotor 5 there are laid chips of magnetpoles 6 with a space 7 between each two adjacent chips. Slits 8 areformed both in each chip of the magnet pole 6 and the magnet yoke on therotor 5. The rotor 5 is a hollow member 9. The shaft 10 of the rotor 5is driven by a driving machine. When the driving machine drives therotor to rotate, the generator starts to generate electricity to supplypower to a load. FIG. 2 is a developed view of the stator windings ofthe present invention. The stator windings are made up of square-waveopen rings. A set of windings consists of three branch windings A1, A2and A3, which corresponding to a pair of opposite magnet poles arearranged to embed in their respective slots on the stator with differentpitches as: crossing 5 teeth then crossing 1 tooth; crossing 3 teeththen crossing 3 teeth; and crossing 1 tooth then crossing 5 teeth. Each12 slots on the stator form a minimum unit. The windings between theunits can be connected in series, parallel or series-parallel mode asrequirement. A plurality sets of windings can be overlapped and embeddedin a same slot. The windings can be connected in series, parallel orseries-parallel. The three-phase windings are arranged in slots on thestator with their respective displacements to obtain three-phase outputfrom the three phase generator. The magnet poles on the rotor arearranged in order of N-S-N-S. FIG. 3 shows the rotor structure, in whichthe magnet poles 6 laid on the rotor and the magnet yoke of the rotorhave slits 8 formed extending axially along the rotor in order to cutoff the current eddy circuits to increase the reluctance and to decreaseiron loss and thereby to reduce the heating. The slits 8 are used forcutting off all the major circulation of current eddy, and the lengththereof is longer than a half of the axial length of the magnet poles.But it can not be too long, otherwise it will reduce the mechanicalstrength of the rotor. The width of the slits 8 is 0.1 mm, which is theoptimum value obtained by tests. The distance between each two adjacentpoles 6 on the rotor equals to the width of the slots on the stator. Andthe thickness of the magnet poles is 7-8 times as much as the width ofthe air gap between the rotor and stator, which is also a optimum valuedetermined by tests. If the poles are too thick it will consume moremagnetic material; if they are too thin the output power of thegenerator will decrease. The two ends of each of the magnet poles 6 areformed into wedge shape and are fixed on the rotor surface withadhesive. The wedge shaped portion are tightly held by wrap edges of therotor. The portion covered by the wrap edges is not more than a quarterof the pole thickness.

The structural features and effects of the present invention will bedescribed in conjunction with the accompanying drawings as follows.

FIG. 2 is a developed view of the stator of the present invention. InFIG. 2, the three branch windings denoted by solid line A1, A2 and A3with different pitches form the phase A winding of the generator.Similarly, the branch windings B1, B2 and B3 denoted by long-dashed lineand the branch windings C1, C2 and C3 denoted by short-dashed line withdifferent pitches form the other two phase windings B and C,respectively.

The number 12,20,30 . . . 3×10n are the serial number of the statorteeth(slots). The A, B and C phase windings of the three-phase generatorare denoted by A, B and C respectively. The winding of each phase ismade up of three square-wave coils with different pitches, which,corresponding to a pair of opposite magnet poles, are arranged to embedin their respective slots on the stator with different pitches as:crossing 5 teeth then crossing 1 tooth; crossing 3 teeth then crossing 3teeth; and crossing 1 tooth then crossing 5 teeth, i.e.,

Phase A(solid line): A1→A1', A2→A2' and A3→A3'

Phase B(long-dashed line): B1→B1', B2→B2' and B3→B3'

Phase C(short-dashed line): C1→C1', C2→C2' and C3→C3'

These windings are sequentially embedded in their respective slots asfollows: for phase A, A1→A1' starts at the first slot, A2→A2' starts atthe second slot and A3→A3' starts at the third slot; the windings forphase B start at the next slot with their negative phase, i.e., B1'→B1starts at the second slot, B2'→B2 starts at the third slot and B3'→B3starts at the fourth slot; and similarly, the windings for phase C startat the next slot relative to the B windings with their positive phase,i.e., C1→C1' starts at the third slot, C2→C2' starts at the fourth slot,C3→C3' starts at the fifth slot. In this way, 120 degree's phasedifference between every two three-phase windings can be obtained.

The winding of each phase comprises three branches(wires) connected inseries as follows:

for phase A winding: (A1→A1')→(A2→A2')→(A3→A3')

for phase B winding: (B1→B1')→(B2→B2')→(B3→B3')

for phase C winding: (C1→C1')→(C2→C2')→(C3→C3')

Thus, the output voltage for each phase equals to the sum of thepotentials induced at the three coils of the winding thereof. If thepotential induced at each coil of the windings is denoted by ΔE, theoutput phase voltage E for the three phases respectively are:

Phase A:E_(A) =ΔE_(A1-A1') +ΔE_(A2-A2') +ΔE_(A3-A3')

Phase B:E_(B) =ΔE_(B1-B1') +ΔE_(B2-B2') +ΔE_(B3-B3')

Phase C:E_(C) =ΔE_(C1-C1') +ΔE_(C2-C2') +ΔE_(C3-C3')

The working process of the three-phase generator of the presentinvention will now be described in conjunction with FIG. 2.

Provided the pole N of the rotor of the generator passes through theposition right under the first, second and third tooth(slot) at the timeT_(A), at this time, since the magnetic flux of pole N are cut byA1→A1', A1→A2' and A3→A3' simultaneously, the voltage for phase Awinding reaches its maximum value

E_(A) =E_(Amax) =ΔE_(A1-A1') +ΔE_(A2-A2') +ΔE_(A3-A3')

The rotor continues to rotate, and when the pole N reaches the positionright under the second, third and fourth tooth(slot) at time TB themagnetic flux of the pole N are cut by windings(wires) B1→B1', B2→B2'and B3→B3' simultaneously, the voltage for phase B windings reaches itsmaximum value

E_(B) =E_(Bmax) =ΔE_(B1-B1') +ΔE_(B2-B2') +ΔE_(B3-B3')

Similarly, when the pole N reaches the position right under the third,fourth and fifth tooth(slot), the magnetic flux of the pole N are cut byphase C winding(wires)C1→C1', C2→C2' and C3→C3' simultaneously, thevoltage for phase C winding reaches its maximum value

E_(C) =E_(Cmax) =ΔE_(C1-C1') +ΔE_(C2-C2') +ΔE_(C3-C3')

During the rotating of the rotor, the pole N moves relative to thewindings on the stators thereby the three phase voltages E_(A),E_(B) andE_(C) are varied continuously. When the pole S reaches the positionright under the first, second and third tooth (slot), a maximum value ofvoltage in the opposite direction, that is the minimum voltage, appearsat the phase A winding:

E_(A) =E_(Amin) =ΔE_(A1-A1') +ΔE_(A2-A2') +ΔE_(A3-A3')

E_(B) =E_(Bmin) =ΔE_(B1-B1') +ΔE_(B2-B2') +ΔE_(B3-B3')

E_(C) =E_(Cmin) =ΔE_(C1-C1') +ΔE_(C2-C2') +ΔE_(C3-C3')

In this way, alternating voltages with a phase difference of 120 degreescan be obtained at the outputs of phases A,B and C.

Compared with the conventional generator of the same output power, thegenerator of the present invention has much less weight and smallersize, and its special windings significantly reduce the consuming ofcopper wire. Further, since its internal resistance is very low, itsexternal characteristic is excellent. The output voltage is almostunchanged even when the load changing, therefore having a good overloadcapacity.

What is claimed is:
 1. An electric generator including:a stator defininga plurality of rectangularly shaped winding slots separated from eachother by sectorially shaped stator teeth; stator windings embedded ineach of said winding slots and defining winding branches; rotorcoaxially mounted for rotation within said stator about a rotor axis andspaced-apart from said stator by an air gap; a magnet yoke disposed on acircumference of said rotor and including a plurality of spaced-apartmagnets thereon, each of said magnets having magnet poles; whereinaxially extending slits are defined at least partially through saidcircumference of said rotor into said magnet yoke and at least partiallythrough an axial length of said magnets thereon; wherein for said statorwindings corresponding to a pair of opposite of said magnetic poles,three of said branch windings belong to one phase of said generator andcomprise square-wave open rings with different pitches, said pitchesselected from a group consisting of (a) crossing five said teeth thencrossing one of said teeth, (b) crossing three of said teeth and thencrossing three of said teeth, and (c) crossing one of said teeth andthen crossing five of said teeth.
 2. The electric generator of claim 1,wherein said winding slots number S, said stator teeth number T, andsaid magnetic poles number P, and S and T are each a multiple of three,and T is a multiple of three times P.
 3. The electric generator of claim1, wherein a distance separating adjacent ones of said magnetic polesequals a width of a said slot.
 4. The electric generator of claim 3,wherein said magnetic poles have a thickness exceeding a width of saidair gap by seven to eight.
 5. The electric generator of claim 4, whereinsaid magnet poles each have two end portions that are formed into awedge shape and are affixed to said circumference of said rotor withadhesive;wherein said portions are tightly retained by wrap edges ofsaid rotor such that said portions have a thickness less than aquarter-thickness of said magnet poles.
 6. The electric generator ofclaim 1, wherein a length of said slits exceeds half of an axial lengthof said magnet poles.
 7. The electric generator of claim 6, wherein awidth of said slits is 0.1 mm.
 8. The electric generator of claim 1,wherein a minimum unit is defined by twelve of said winding slots withsaid stator windings embedded therein, and said windings between saidunits are connectable in a configuration selected from the groupconsisting of (a) series, (b) parallel, and (c) series-parallel.
 9. Theelectric generator of claim 8, wherein a plurality of sets of saidwindings are overlapped in multiple layers and embedded in said slots ata same position, said windings being connectable in a configurationselected from the group consisting of (a) series, (b) parallel, and (c)series-parallel.
 10. The electric generator of claim 8, wherein thereare three phase windings embedded in respective ones of said slots withrespective displacements.
 11. The electric generator of claim 8, whereineach layer of a winding in one of said strator slots comprises a singleconducting wire.
 12. The electric generator of claim 3, wherein a lengthof said slits exceeds half of an axial length of said magnet poles. 13.The electric generator of claim 4, wherein a length of said slitsexceeds half of an axial length of said magnet poles.
 14. The electricgenerator of claim 5, wherein a length of said slits exceeds half of anaxial length of said magnet poles.
 15. The electric generator of claim 9wherein there are three phase windings embedded in respective ones ofsaid slots with respective displacements.